Touch panels or touch screens are present in many different types of common modern electronic devices, such as cellular telephones, tablet computers, portable music and video devices, personal digital assistants, portable gaming devices, and so on. In these electronic devices the touch screen is part of the user interface of the device. The touch screen typically includes a display, touch sensors, and a touch controller. The touch sensors are typically some sort of transparent sensor array, such as an ultrasonic, resistive, vibration, or capacitive sensor array, that is attached to or formed as an integral part of the display. When a user touches the sensor array either with a finger or a stylus, the sensor array generates corresponding electronic sensor signals that are provided to the touch controller. From these sensor signals, the touch controller detects the occurrence of a touch or touch point.
The touch controller also determines the type of “touch event” to be associated with the touch point, along with various characteristics of the touch event, and provides this information to processing circuitry in the electronic device. The processing circuitry operates in response to this information to allow a user to control the electronic device through these touches or touch points on the touch screen. The touch controller captures frame data from the touch sensors and processes this frame data to detect the presence of a touch point and the type of touch event (i.e., touch-in event, touch-out event, touch-motion event) associated with the touch point. This processing is typically referred to as touch frame processing and through this processing the touch controller generates touch information including the type of touch event and the location of the touch event on the touch screen. Touch frame processing also includes detecting or recognizing particular gestures by a user on the touch screen and controlling the electronic device accordingly. For example, the ubiquitous “swipe gesture” is commonly used to flip from one page to another in a document or to change to different sections on a desktop or home screen of an electronic device.
A typical capacitive touch sensor is formed by an array of conductive force lines Ci and sense lines Lj that are arranged orthogonal to one another to form a matrix or array of touch or sensor nodes CiLj. The force lines Ci may be viewed as column lines and the sense lines Lj as row lines, where the array includes “i” force lines and “j” sense lines. Patterns other than mere orthogonally arranged conductive lines are typically utilized, such as diamond-shaped patterns, as will be appreciated by those skilled in the art. The sensor nodes collectively detect the touch information, which includes location information, the touch event type (i.e., touch-in event, touch-out event, or touch-motion event), and other parameters like pressure, size, and so on, as will be appreciated by those skilled in the art.
The sensor nodes CiLj detect the touch information through variations of four “fringing” capacitances associated with each sensor node Ci,Lj when a user touches the sensor proximate the sensor node. This is typically referred to as “mutual sensing” since the touch by the user affects the capacitance between adjacent nodes or the “mutual capacitance” between the nodes. In addition, current capacitive touch screens also utilize self-capacitance (i.e., the current at each sensor node to ground), which is affected by the presence of a user's finger or other suitable device positioned within a sensing range from the surface of the touch screen but not touching the touch screen. In this way, the position of the user's finger above the touch screen can be detected. With such touch screens three-dimensional sensing is possible since both touches on the touch screen (i.e., two-dimensional touches) and the position of a user's finger above the touch screen (i.e., a third dimensional touch) can be sensed and utilized in controlling the electronic device containing the touch screen. Accordingly, three-dimensional gestures may be detected and utilized in controlling the electronic device.
There is a need for improved three-dimensional gesture recognition systems and methods for touch screens.